Narrator (April Hobart, CXC): GRS 1915+105, or GRS 1915 for short, is a special system. Not only does it contain a black hole some 14 times more massive than the Sun in orbit with a companion star, it also has a heartbeat. Or, more exactly, it gives off X-ray pulses that resemble the pattern of a human heart, though on a much slower scale. By monitoring this system with NASA's Chandra X-ray Observatory and the Rossi X-ray Timing Explorer, astronomers were able to pick out a spike of X-rays every 50 seconds or so. Researchers have determined that this heartbeat is due to the ebb and flow of material as it circles the black hole. This result gives scientists more insight into how black holes regulate their intake and control their growth.